Re: [TenTec] Centurion Squeal and Oscillation

[Robert & Linda McGraw K4TAX <RMcGraw@Blomand.Net>]

I don't recall the details of the original post but I seem to remember that 
the problem was on 40M and did not appear on other bands.  This raises the 
question of how does the fan being loose relate to 40M only?
As to input cable length, I'd expect that certain lengths, depending on 
source Z  loading, Orion output vs. Omni VI output, might have some effect 
relating to a feedback path.  On the other hand, in receive the Centurion 
input should be disconnected via the T/R relay.  Haven't looked at the 
schematics.
While the problem seems to be corrected, the explanation, approach and 
application does not seem to be technically satisfied to me.  Need to look 
into it a bit further to satisfy my quest for information.
73
Bob, K4TAX


----- Original Message ----- 
From: "Dave K2DP" <k2dp@charter.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Monday, October 10, 2005 11:17 PM
Subject: Re: [TenTec] Centurion Squeal and Oscillation


> Hi Hank,
>
> As a new owner of a 5 year old Centurion amp, I am curious to know the age
> of your amp ? I am running the Centurion with my Omni 6 Plus and have not
> seen either of the problems you encountered. However, I have lots of coax
> running around the amp and between the exciter, etc.
>
> 73 and look forward to hearing from you. Glad to know that TenTec and the
> list here were able to help solve your problem.
>
> 73,
> Dave, K2DP, St. Louis
> ----- Original Message ----- 
> From: "Henry Pfizenmayer" <pfizenmayer@worldnet.att.net>
> To: <tentec@contesting.com>
> Sent: Monday, October 10, 2005 10:11 PM
> Subject: Re: [TenTec] Centurion Squeal and Oscillation
>
>
> > FWIW _ It appears with the help of several folks on this reflector and 
> > the
> > AMPS reflector the Centurion oscillation problem on 40 meters is 
> > resolved.
> > It also appears the "squeal " is fixed but may require a little more time
> > to be 100 percent sure.
> >
> > Tentec service says the squeal is coming from the fan bearings and
> > recommends you take the label off the fan and tighten the screws behind
> > the label . This is a weird one as the pitch does not change when you 
> > turn
> > off the amp and the fan is running down - my fan spins  for about 74
> > seconds after turn off- TT says the one they timed was more like 3
> > minutes, so I may have marginal bearings. This operation is a little bit
> > of a pain as the  fan label and screws are right behind the RFC and
> > parasitic suppressor assy, so you have to remove the tubes and the rfc
> > assy to get to the fan.
> >
> >  The solution for  the oscillation on 40 meters was to increase the 
> > length
> > of coax between the Orion and the Centurion. One person also suggested a
> > W2DU type ferrite bead current mode "isolator". I had a Wireman balun 
> > good
> > to 160 so I tried that (that added about 3 feet to my already 4 foot long
> > jumper) and the oscillation stopped, and all bands were stable.
> > I wondered if maybe the real change was just the extra cable length so I
> > made up a 8 foot RG8x jumper and the amp was still stable all bands. When
> > I called Tentec to tell them about the solution - they said they normally
> > use about a 8 foot cable so they had never seen what I encountered with a
> > short interconnect.
> >
> > So In summation.
> >
> >
> > Squeal - Tighten the screws under the label on the fan
> >
> > 40 meter oscillation - be sure you have at least 8 feet of  RG8 or RG8X
> > cable between the exciter and the. amp
> >
> > Thanks to all for the suggestions - looks like I am back in business.
> >
> > Hank K7HP
> >
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